Bake in shell-compl generation

Therefor we need to have at least clap 2.16.1.

We bake this into libimagrt::runtime::Runtime, so all binary crates
should automatically have it.

libimagrt/Cargo.toml

@@ -14,7 +14,7 @@ repository    = "https://github.com/matthiasbeyer/imag"
 homepage      = "http://imag-pim.org"
 
 [dependencies]
-clap = "2.*"
+clap = ">=2.16.1"
 env_logger = "0.3"
 toml = "0.2.*"
 log = "0.3"

libimagrt/src/runtime.rs

@@ -57,6 +57,9 @@ impl<'a> Runtime<'a> {
      */
     pub fn new(cli_spec: App<'a, 'a>) -> Result<Runtime<'a>, RuntimeError> {
         use std::env;
+        use std::io::stdout;
+
+        use clap::Shell;
 
         use libimagstore::hook::position::HookPosition as HP;
         use libimagstore::hook::Hook;
@@ -79,6 +82,15 @@ impl<'a> Runtime<'a> {
 
         Runtime::init_logger(is_debugging, is_verbose, colored);
 
+        match matches.value_of(Runtime::arg_generate_compl()) {
+            Some(shell) => {
+                debug!("Generating shell completion script, writing to stdout");
+                let shell = shell.parse::<Shell>().unwrap(); // clap has our back here.
+                cli_spec.gen_completions_to("fakename", shell, &mut stdout());
+            },
+            _ => debug!("Not generating shell completion script"),
+        }
+
         let rtp : PathBuf = matches.value_of("runtimepath")
             .map_or_else(|| {
                 env::var("HOME")
@@ -255,6 +267,15 @@ impl<'a> Runtime<'a> {
                 .help("Set editor")
                 .required(false)
                 .takes_value(true))
+
+            .arg(Arg::with_name(Runtime::arg_generate_compl())
+                .long("generate-commandline-completion")
+                .help("Generate the commandline completion for bash or zsh or fish")
+                .required(false)
+                .takes_value(true)
+                .value_name("SHELL")
+                .possible_values(&["bash", "fish", "zsh"]))
+
     }
 
     pub fn arg_names() -> Vec<&'static str> {
@@ -302,6 +323,10 @@ impl<'a> Runtime<'a> {
         "editor"
     }
 
+    pub fn arg_generate_compl() -> &'static str {
+        "generate-completion"
+    }
+
     /**
      * Initialize the internal logger
      */